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Zone troubles again

OK guys, you came through for me last time so I am looking for your feedback once again.

Now that we have turned the corner towards Fall here in DFW the problem we are now dealing with is humidity. 55%-65% day in and day out. While temp. outside are still pushing 90 and we have the house zones all set at 76 we can not rid the home of the humidity.

I feel this has to do with the 5 ton system not moving enough air? Also, early on, the company "by-passed" the units air sensor and started controling the zones by the thermostats. This is a multi-speed unit, total of three stages now (see string) so one would thing the system would be running in the first stage all most no stop to remove humidity?

I am still looking for the name of a independent HVAC group in the DFW area that can help me make sense of every thing.

Thanks to everyone here for helping level the playing field, I can only fear what is going to happen when I turn on the heat? I still think moving enough air is going to be the problem, by the company is saying I don't need the same amount of heat as I do air and the 5 ton will be fine?

I will try and add pictures but was hoping there was enough in the prevoius threads. The only thing missing is the new 2 ton unit.

It is an Amana High Eff. 14 (2 ton AC / no heat)

They have this unit confg. as a third stage, it only kicks in when 2nd stage on the 5 ton has been running for 15 mins. or more.

So, this time of year it never kicks in, that I know of.

All the duct work was replaced during install and the system was designed around three zones using the 5 ton. The addtional 2 tons was added because the house was not cooling during the peak summmer months.

I agree that you should need less than the 5 ton capacity for heating...thats the norm in many parts of the country.

Usually humidity removal is improved by lowering the cfm across the coil. The coil runs colder and air moves across it slower allowing for increased moisture removal onto the coil.

Do you have a feel for what stage the cooling is running in most of the day?

There are thermostats that control dehumudification by running the A/C with a lower blower speed. I don't know if your eguipment can make that happen but it "might" help.

Usually undersized cooling systems do a good job of humidity removal becouse they have to run more to keep up. If the air flow across the coil is excessive that will greatly reduce moisture removal ability (latent heat removal).

I hope that helps!

Joe

"When you perceive zoning not as a bandage but as an enhancement, you truly understand the dynamics and limitations of forced air heating and cooling"

From what I can tell, the unit kicks into it's first stage (3-5 mins. max)and only runs for a short period of time. It does this multiple times each hour, I assume it is trying to meet the needs as each therm. calls for air.

Could the unit be short cycling? The more it runs, through out the day, the higher the humidty in the house gets. Ther are days were it drives the humidity in the house well above the humidty levels out side!

Man,,,,, Unless you have 2 x 12 walls and R40 in the attic, I don't see how they can make a 5 ton unit satisfy 32000 cubic feet of living area in Dallas Texas. If you have 2 x 4 walls and 10" of insullation in the attic, your probably going to need every bit of 8 tons capacity!

You just cant cram that much insulation in a 2x4 wall. A 2x4 wall with bat fiberglass/cellulose insulation is only R12 or so.

Quick check:
Get the house as cold as you can then shut off the unit.
Read the thermostat temperature. (average all the thermostat readings you have in the house) Wait 1 hour. Read the thermostat temperature. If it has increased more than 2.5 degrees,,,(again,, an average reading),,,,, your at least 3 tons short! It is very cloudy here today and you won't have some rooms being real radical in temperature shift due to sun light.

Of course a good heat load calculation should be your next step but the "Quick check" should give you an idea of what your facing.

As far as I know, each unit has two fan speeds. I have no real way of telling what speed they are running in at any given time. Is there a way I can check? Plus, with the zone system, it seems to blow hard in the office zone for a min or so then it sounds like the by-pass kicks in or the dampers adjust the air flow.

The units site outside my home office so I hear the 5 ton unit kick on and off each time. It runs for 3-5 mins. then shuts down. If you get a chance to read the entire thread, you will see the second 2 tons was added later. The original load calculation are in the thread also. The unit just kicked in @ 2:10 my time and just shut down @ 2:16

The way the explained the extra unit was added to meet the demands of the zones during peak load. The 2 ton unit does not run on any set timer or pattern. I can onlyt get it to kick in by driving all the therms. down 6-10 degrees OR if its warm enough outside, by getting the main 5 ton to run in 2nd stage for more the 15 mins. (same result, differnt wording)

No the house is not super insulated in fact the house was built in 1988. Prior to adding the addtional 2 tons, the company tried to adjust the load by blowing in an addtional 6" of insulation, then suggested I change out my windows.

The insulation was OK (couldn't hurt) but spending more money on new windows?????